An antireflective film is employed in general to lower the refractive index with the use of the optical interference principle so as to prevent a decrease in contrast or image transfer caused by the reflection of outside light in image display units such as a cathode-ray tube (CTR), a plasma display panel (PDP), an electro luminescence display (ELD) and a liquid crystal display (LCD).
Such an antireflective film can be constructed by forming a hard coat layer and an antiglare hard coat layer on a substrate and further forming a low refractive index layer having an appropriate layer thickness thereon. From the viewpoint of productivity, it is preferable to form each layer by the wet coating.
As materials usable in the wet coating, there have been known fluorine-containing copolymers having a low refractive index (see, for example, JP-A-2003-26732). However, these fluorine-containing copolymers suffer from a problem that uniform coating cannot be achieved thereby when applied on an antiglare hard coat layer having peaks and valleys.
On the other hand, it has been proposed to add a surfactant to a coating composition so as to lower repellency and so on and achieve uniform coating. This proposal is based on the mechanism that, by adding a surfactant to a coating, the surface tension is lowered and wetting properties on the subject to be coated so that a change in the surface tension in the course of the coating layer formation is lessened or lowered and heat convection is prevented, thereby improving the layer uniformity (KOTINGUYO TENKAZAI NO SAISHIN GIJUTSU, supervised by Haruo Kiryu, CMC, 2001).
JP-A-11-228631 and JP-A-2004-4444 report a copolymer having a polysiloxane block copolymer introduced thereinto with the use of a silicone macro azo initiator and use of the copolymer in an antireflective layer. According to this method, uniform face figure can be obtained even in a face having peaks and valleys. In the case where the amount of the silicone macro azo initiator is increased so as to elevate the polysiloxane content in producing the polysiloxane-containing copolymer, however, the initiator remaining or a component produced by radical coupling of the remaining initiator can be hardly eliminated. Accordingly, the amount of the polysiloxane component to be introduced cannot be always easily controlled.
As described above, it has been required to develop a technique whereby the coating properties of a fluorine-containing copolymer can be improved without damaging layer qualities by using an additive which allows the regulation of the amount of polysiloxane to be introduced.